Background

Once in the marine environment, many chemicals especially heavy metals tend to accumulate within the tissues of living aquatic organisms, getting at higher amounts as they move up the food chain (Bat, 2014). As each organism consumes its prey, it takes in a large part of the heavy metals that are accumulated in the prey’s tissues. Toxic metals have the propensity to pile up in benthic sessile organisms, which in turn may enter into the human metabolism owing to consumption leading to grave health hazards. A mussel filters many times its own body weight in particles as food during the course of its life. Bioaccumulation of heavy metals occurs if the rate of uptake by the mussels exceeds the rate of elimination. As a result, the mussels end up with a much higher amount of heavy metals in its own tissues than were in the ambient (Bat, 1996). Heavy metals are steady and consistent ambient pollutants of marine waters. Essential heavy metals as Cu and Zn whichever are needed for the metabolism of a living organism, whereas non-essential ones as Hg, Pb and Cd may show very high toxicity likewise at nominal amounts sub specific circumstances, thence requiring routine biomonitoring of sensitive marine costs (Bat et al., 2009).

Considered mussels are potential bio-monitor organisms, inasmuch as some alteration in system metal level get about by a temporary or geographic change in the surrounding bioavailability of the heavy metals (Bat and Öztekin, 2016). With respect to using of the acceptance of M. galloprovincialis as a bio-monitor organism in the Black Sea there are many studies reviewed by Bat (2014). The current work thus objective to appraise heavy metal amounts in M. galloprovincialis from Sinop coasts of the Black Sea with regards to human consumption.

1 Materials and Methods

The specimens of mussels were captured by diving at a depth of nearly 20 m, where their settlements were outside dense. They were carried directly from the sampling station (Figure 1) to the Hydrobiology Laboratory and afterwards they were put in uncontaminated reference seawater in tanks (20x20x25 cm) for a day to clean the substances in alimentary canals (Bat et al., 1999). Ensuing removal of the bowel contents, the individuals of mussels were dissected out (Bernhard, 1985) accordingly their sizes and were separated into edible part, and kept in deep freezer at –21°C for metal analyses. The frozen tissue samples of mussels were thawed, rinsed in distilled water and dried in blotting paper. Known weights of the mussel samples were put to 100 ml volumetric flasks for digestion according to UNEP (1984; 1985). Concentrations of Hg, Cd, Pb, Cu and Zn in the edible tissue samples of the mussels were performed with m-AOAC 999.10 Inductively Coupled Plasma/Mass Spectrometer (ICP/MS) technique by certificated Environment Industrial Analysis Laboratory Services Trade Company (TS EN ISO IEC 17025 AB-0364-T).

2 Results

Cu and Pb were determined in maximum levels came after Zn. Hg and Cd displayed the minimum levels in all samples. The mean Hg, Cd, Pb, Cu and Zn levels in edible tissues of the mussels were 0.02±0.009 mg/kg, 0.03±0.01 mg/kg, 0.08±0.03 mg/kg, 1.12±0.3 mg/kg and 11±3 mg/kg wet wt., respectively (Figure 2). It is deduced that the Mediterranean mussels M. galloprovincialis are convenient biomonitors to specify alterations in heavy metal pollution in the Black Sea coastal area. The results acquired in the current work on heavy metal levels in the mussel samples show that these amounts were lower than the proposed standards. It is worth mentioning that consumption of the mussels from the Sinop seashores of the Black Sea may not potential state of health threats to people at the time of the work.

3 Discussion

The amount of chemicals inclusive heavy metals in the marine coastal environment and their effects requirement to be appraised considering the influences and menaces to the ecosystem in Article 8 (1) (b) (ii) of Directive 2008/56/EC. Chemicals in seafood including mussels for people consumption do not passed over amounts established by European Community regulations or other relevant standards. Heavy metals in mussels from Sinop seashore of the Black Sea, the literature (Table 1) show highly variable results.

Studies conducted on Sinop coasts show that Zn values are generally similar to each other between 1990 and 2014. Only two studies had higher values than the others. An increase was observed in the samples taken from 1997-1998 (Topcuoglu et al., 2002), but reached the highest level in the samples collected in 2005-2006 (Turk Culha et al., 2007). In the Sinop coast, the maximum Cu value was 6.03 μg/g wet wt. (Unsal et al., 1992) and minimum value was 0.039 μg/g wet wt. before 1990 (Öztürk, 1991). The annual fluctuation has been observed in Cu values in studies conducted in Sinop coast.

It is seen that the Pb values decrease over years in the mussel samples taken by various researchers from the Sinop coasts. The maximum value was found 8.946 μg/g wet wt. before 1990 (Öztürk, 1991), it is also observed that the Pb values decrease towards 2014 in the results of the studies. Cd values were found to be high in studies conducted between 1990 and 2006, but it appears to have fallen after 2006. Cd value was found minimum<0.02 μg/g wet wt. (Arıcı and Bat, 2016) and the maximum 0.86 μg/g wet wt. (Öztürk, 1991).

It is seen that the Hg values measured in studies conducted in Sinop were generally below the level of measurement (Das et al., 2009; Arıcı and Bat, 2016). In the current study, the Hg value was found to be 0.02±0.009 wet wt., well below the limit values.

In general, heavy metals can make their way to marine coastal environment via uncontrolled routes, such as rivers, industrial and domestic discharges, touristic activities and ships. It is necessary and helpful that heavy metals, which affect people health negatively route dregs in seafood, should be monitored (Bat, 2014).

Authors’ contributions

LB designed and conducted the experiment; prepared the samples for metal analysis, evaluate data and finalized the manuscript. EA performed critical review of the manuscript. AÖ contributed to the paper by processing the data and made figures and table. ÖY and FÜ contributed to the paper by collecting samples and help to prepare them for metal analysis. All authors read and approved the final manuscript.

Acknowledgments

This work was carried out at the University of Sinop, Fisheries Faculty, Department of Hydrobiology. A part of this study was presented as poster in the 3^rd International Symposium on EuroAsian Biodiversity (SEAB-2017), Belarusian State University, Faculty of Biology, 5-8 July 2017, Minsk, BELARUS.

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